Pen



FIG. 1 is a front elevation view of a pen showing my new design;

FIG. 2 is a top elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof; and,

FIG. 5 is an exploded front elevation view thereof. 

The ornamental design for a pen, as shown and described. 